1. Field of the Invention
The present invention relates to a method and apparatus which allows an installer to quickly and accurately point, and fine tune the pointing of an antenna, without the need of utilizing expensive monitoring equipment.
2. Description of the Related Art
Conventional methods of pointing a satellite antenna dish to optimally transmit and receive signals from a geo-synchronous satellite involve mounting the antenna on the intended platform, pointing the antenna in the general direction of the satellite, monitoring the signal strength of the signal received by the antenna (which is transmitted by the satellite) and varying the direction of the antenna in an effort to maximize the strength of the received signal. The position of the antenna which results in maximum received signal strength is selected as the permanent position. This technique is known, as “peaking” the signal.
In one example of performing this technique, the ground terminal (also referred to as the satellite terminal or “ST”), which is located at a remote location and includes the antenna to be aligned, is provided with the capability of generating a voltage signal having a level indicative of the strength of the signal received by the antenna. Typically, the voltage signal is a DC signal and can be measured utilizing a voltmeter or other signal strength indicator. Accordingly, when utilizing the foregoing alignment technique, the operator monitors the strength of the voltage signal, while adjusting the direction of the antenna and selects the position of the antenna corresponding to the highest obtainable level of the voltage signal as measured by the voltmeter. It is noted that in existing satellite receiver/transmitter systems, the value of the signal strength of the voltage signal rises as the antenna is pointed toward the satellite source and falls as it is moved away from the satellite source. Of course, the opposite is also possible.
While the foregoing method allows for the antenna installer to quickly point the antenna in the general direction of the desired satellite, it does not allow the antenna operator to fine tune the pointing of the antenna. In other words, the antenna installer cannot confirm that the maximum possible signal has been received. Indeed, the antenna installer simply adjusts the antenna position until a predetermined acceptable signal strength is received. However, the installer has no means of confirming whether or not this is the maximum possible signal available. This is due to the fact that the directivity of the antenna is relatively flat in the area defining the peak of the antenna pattern. As such, it is difficult to discern the pointing error (i.e., the shift from actual peak). It is noted that while it would be possible for the installer to confirm receipt of the maximum signal strength if the installer was provided sophisticated signal analysis equipment, such as a spectrum analyzer, it is not possible to do so as the costs of providing such equipment to the operator are prohibitive.
Accordingly, there remains a need for an apparatus that allows an antenna operator to quickly and easily determine whether the antenna has been positioned so as to achieve optimum signal strength of the received signal transmitted by the satellite, without the need for the operator to have access to sophisticated signal analysis equipment. It is further noted that the existing antenna pointing techniques are not likely to achieve the stringent antenna pointing requirements/tolerances (e.g., <0.2 degrees) that can be required for successful operation of broadband, multimedia satellite communication systems with terminals employing a receiving antenna having a reduced diameter (i.e., a small antenna). This is especially true given the fact that typical satellite systems uplink at higher frequencies with narrower beam widths, thus pointing errors measured by the receiver are amplified in the transmit direction.